Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<iostream>
#include<vector>
using namespace std;

char maze[51][51];
int reached[51][51];
int H, W;

void dfs(int x, int y, int step = 1) {
    if(maze[y][x] != '.') return;
    if(reached[y][x] <= step) return;
    if(x < 0 || W <= x || y < 0 || H <= y) return;

    reached[y][x] = min(reached[y][x], step);

    dfs(x+1, y, step+1);
    dfs(x-1, y, step+1);
    dfs(x, y+1, step+1);
    dfs(x, y-1, step+1);
}

int main() {

    cin >> H >> W;
    int cnt = 0;
    for(int i = 0; i < H; i++) {
        for(int j = 0; j < W; j++) {
            cin >> maze[i][j];
            reached[i][j] = 1e9+1;
            if(maze[i][j] == '#') cnt++;
        }
    }
    dfs(0, 0);

    if(reached[H-1][W-1] == 1e9+1) cout << -1 << endl;
    else cout << H * W - reached[H-1][W-1] - cnt << endl;

    return 0;
}